1. Field of the Invention
This invention relates to a target assembly adapted for use in diode sputtering systems and, more particularly, to an improved sputtering selected material therefrom in a controlled erosion pattern.
2. Description of the Prior Art
Triode sputtering apparatus, means and systems are well known in the prior art. Diode sputtering apparatus, means and systems are, likewise, well known in the prior art. The triode sputtering apparatus utilize separate anodes and cathodes for producing a source of electrons utilized in the formation of the plasma and the generation of the sputtered ions from the target material. A description of the known sputtering apparatus, means and systems and methods thereof, including use of magnetically enhanced triode target assemblies, is disclosed in U.S. Pat. No. 4,155,825 and U.S. Pat. No. 4,404,077, both of which were issued to the inventor of the present invention.
The use of a magnetically enhanced diode sputtering device, including magnetic means for establishing a magnetic field with the lines of force thereof extending over and passing through the sputtering surface of a target assembly, is disclosed in U.S. Pat. No. 4,265,729. In such magnetically enhanced diode sputtering devices, the magnetic means establishes a closed loop configuration of the lines of force across the target surface, wherein the closed loop configuation of the lines of force has at least some nonlinear portions. Separate flexible magnetic means may be utilized for enhancing the uniformity of magnetic field along the nonlinear portions in order to control the shape of the closed loop configuration of the lines of force through the target surface.
The known prior art devices which utilize the magnetic field to enhance sputtering of a target is illustrated in FIG. 1 identified as "Prior Art." In such devices, the target material 20 is eroded in a manner such that a conical surface 22, having a V-shaped cross section 24, is produced by the closed-loop configuration or arcuate-shaped configuration of the lines of force emanating from magnets 28 and 30. The results of the known prior art devices is to erode the target material in a conical-shaped method, resulting in a substantial portion of the target material 20 remaining unsputtered. This phenomenon results from the fact that, for sputtering to occur, the electric field E must cross the magnetic field B at substantially 90.degree. to form a B.times.E field. As the conical-shaped surface 22 of the target material erodes in a conical shape, a trench forms in the target surface which results in a portion of the target material not being utilized. By use of moving magnets under the target surface, the trenching effects can be reduced.
The relationship which is required for establishing sputtering conditions is set forth in detail in U.S. Pat. Nos. 4,155,825 and 4,404,077, referenced hereinabove, and need not be set forth here in detail.